Thoracic Outlet Syndrome: The Three Types Explained

All information in this blog is supported by NHS clinical guidance and peer-reviewed research. There is currently no dedicated NICE guideline for this condition, but NHS clinical guidance and current evidence are used throughout. Reference numbers appear throughout, with the full list at the bottom of the page.

What Is Thoracic Outlet Syndrome?

Thoracic outlet syndrome (TOS) is where nerves or blood vessels near the top of the ribs get squashed, usually affecting one arm and hand. ¹ It happens in a tight anatomical space called the thoracic outlet, the narrow gap between your collarbone, first rib, and the surrounding muscles, through which the nerves and blood vessels supplying your arm must pass.

TOS remains something of a diagnostic enigma, an uncommon cause of upper limb symptoms, but one with real potential to cause chronic pain and disability, meaning it's worth considering when more common explanations for arm symptoms don't quite fit. ² It's often linked to having an extra rib, known as a cervical rib. ¹

The Three Types of Thoracic Outlet Syndrome

TOS has three subtypes: neurogenic (nTOS), venous (vTOS), and arterial (aTOS). ² Each involves a different structure being compressed, and each has a genuinely different presentation, risk profile, and treatment approach.

1. Neurogenic Thoracic Outlet Syndrome (nTOS)

This is by far the most common form. Over 90% of all TOS cases are neurogenic, caused by compression of the brachial plexus, the network of nerves running from the neck into the arm. ² It results from compression of the brachial plexus between the scalene muscles of the neck and the first rib, leading to disabling upper extremity pain and paraesthesia. ³

Typical symptoms: arm numbness, a sense of heaviness or fatigue, diffuse arm ache, and tingling in the hand, often with an insidious, gradual onset that can be subtle and easily mistaken for other conditions. ²

2. Venous Thoracic Outlet Syndrome (vTOS)

This occurs when the subclavian vein, the major vein draining blood from the arm, becomes compressed within the thoracic outlet. It's far less common than neurogenic TOS, but it can present suddenly and seriously.

Typical symptoms: swelling, heaviness, and a bluish discolouration of the arm, sometimes developing rapidly. This can indicate a blood clot forming in the vein, a genuine medical emergency, covered further in the red flags section below.

3. Arterial Thoracic Outlet Syndrome (aTOS)

The rarest of the three types, this involves compression of the subclavian artery, the major artery supplying blood to the arm, often associated with a cervical rib or other bony abnormality.

Typical symptoms: coldness, paleness, and pain in the arm or hand, sometimes alongside a noticeably weaker pulse, and can also present acutely if a clot or aneurysm develops.

Comparison Table: The Three Types of TOS

Feature	Neurogenic (nTOS)	Venous (vTOS)	Arterial (aTOS)
Structure compressed	Brachial plexus (nerves)	Subclavian vein	Subclavian artery
Proportion of cases	Over 90% ²	Around 36% of surgical cases ⁴	Around 24% of surgical cases ⁴
Typical onset	Gradual, insidious ²	Can be sudden	Can be sudden
Key symptoms	Numbness, heaviness, ache, tingling in hand ²	Swelling, heaviness, bluish discolouration	Coldness, paleness, weak pulse
Who's most affected	Often associated with repetitive overhead activity, poor posture, previous neck trauma	Often associated with repetitive overhead arm use (e.g. swimmers, weightlifters), or "effort thrombosis"	Often associated with a cervical rib or bony abnormality
Urgency	Usually non-urgent, but disabling if untreated	Can be a medical emergency (clot risk)	Can be a medical emergency (clot or ischaemia risk)
First-line treatment	Physiotherapy and exercise rehabilitation	Medical assessment, often anticoagulation, sometimes surgery	Medical assessment, often surgical decompression
Surgery typically needed?	Reserved for cases not responding to conservative care	Frequently required	Frequently required

Who Is at Risk?

Most patients with TOS are female, with research showing 65% of cases occurring in women. ⁴ Beyond this, risk factors differ somewhat by type, but commonly include:

• Repetitive overhead arm activity, such as swimming, weightlifting, painting, or certain manual occupations

• Poor posture, particularly rounded shoulders and forward head posture, which narrows the thoracic outlet space (this connects directly to the postural conditions and upper crossed syndrome content covered elsewhere on our site)

• A cervical rib or other anatomical variation, an extra rib or fibrous band present in some people from birth, increasing the risk of arterial and neurogenic TOS in particular

• Previous neck or shoulder trauma, including whiplash injuries, which can alter the muscles and tissue around the thoracic outlet

• Heavy backpack or bag use, placing sustained downward pressure on the shoulder girdle

• Pregnancy and significant weight gain, which can alter posture and the space available within the thoracic outlet

What to Look Out For

This is one of the genuinely important sections of this blog, because whilst neurogenic TOS is rarely an emergency, the vascular types can be. Seek urgent medical attention if you have sudden breathlessness, sharp chest pain that may be worse when you breathe in, and a cough or coughing up blood, as these could be signs of a blood clot caused by thoracic outlet syndrome, which can be life threatening if not treated quickly. ¹ PubMed Central

Other features requiring urgent assessment include:

• Sudden swelling, heaviness, or bluish discolouration of the arm (possible vTOS with clot)

• Sudden coldness, paleness, or significant pain in the arm or hand (possible aTOS)

• A noticeably weaker or absent pulse in the affected arm

• Rapid worsening of symptoms

For non-urgent neurogenic symptoms, a GP will usually check your arms, chest, and neck to look for possible causes, and may refer you for an X-ray or other tests such as a CT or MRI scan. ¹

How Is It Diagnosed?

Diagnostic elements include pain (present in 99% of cases), symptoms made worse by raising the arm (97%), tenderness on palpation of the scalene and subcoracoid area (96%), and numbness, tingling, or weakness in the arm or hand (94%), alongside a positive specific provocation test. ⁵ Posture and shoulder blade assessment formed part of the examination in over half of studies reviewed, though notably, mobility of the first rib was assessed in only a minority of cases, and breathing assessment even less often, both genuine gaps in typical clinical practice. ⁵

How We Can Help: Treatment for Each Type

Neurogenic TOS (nTOS): The Type We Can Help With Most Directly

Osteopathic manual techniques and manual therapy: manual therapy formed part of treatment in the majority of studies reviewed, working alongside exercise to address restriction in the scalene and pectoral muscles, the scapula, and the cervical and thoracic spine. ⁵ This connects directly to the thoracic mobility work covered in our neck pain and stiffness blog, restoring movement here can genuinely reduce the compression contributing to nTOS.

Deep tissue and sports massage: activation and release work targeting the scalene muscles is considered one of the most important elements of conservative management, helping to normalise function of the thoracic outlet. ⁷

Targeted exercise: research found stretching, strengthening, neural mobility work, and diaphragmatic breathing were the most common and effective exercise components, with the scalene and pectoral muscles being the most frequently targeted for stretching, and scapular stabilisation the most common strengthening focus. ⁵

Specific exercises with good supporting evidence:

• Scalene release/stretch: gently pressing your forehead against your palm for around 5 seconds without creating movement helps activate and normalise the anterior scalene muscle, with similar techniques used for the middle and posterior scalene by pressing sideways and backwards respectively. ⁷

• Pectoralis minor and chest stretching: stretching of the pectoralis minor has formed part of established rehabilitation protocols for nTOS since the earliest described programmes, helping open the space beneath the collarbone. ⁸ Dovepress

• Scapular stabilisation and strengthening: strengthening the posterior spinal muscles, levator scapulae, and isometric work for the serratus anterior helps improve postural support around the thoracic outlet. ⁸

• Nerve gliding exercises: exercises including nerve gliding, postural work, and shoulder girdle exercises have been found effective in improving neural mobility and relieving tension in the brachial plexus. ⁹

• Diaphragmatic breathing: this helps reduce overactivity of the scalene muscles, which act as secondary breathing muscles when overused, directly reducing one of the key contributors to nTOS compression.

  
  

An important caution: patients should generally avoid intensive aerobic activities, as these lead to exertional breathing and subsequently increase activity of the scalene muscles, potentially worsening symptoms. ⁹ This is genuinely useful, practical guidance worth discussing with your practitioner.

Surgery, including first rib resection or scalenectomy, is reserved for nTOS that fails to respond to a thorough course of conservative treatment.

Venous TOS (vTOS): Why We Work Alongside Medical Teams

Given the genuine risk of blood clot formation, vTOS requires prompt medical assessment, often involving anticoagulation medication and frequently surgical decompression. Surgery for vTOS in UK practice showed the highest rates of symptom resolution among the three types. ⁴ Once medically cleared and any clot risk addressed, manual therapy and exercise can support recovery of movement and function, working alongside your vascular team rather than as a standalone first-line treatment.

Arterial TOS (aTOS): The Type Requiring Surgical Assessment

Surgery for aTOS frequently involves decompression of the thoracic outlet. ⁴ Surgical approaches can include removal of the first rib and division of the affected scalene muscles, with the artery then inspected for any degeneration, dilation, or aneurysm. ¹⁰ As with vTOS, conservative manual therapy and exercise have a role in supporting recovery once the vascular issue has been appropriately managed, not as an alternative to necessary medical or surgical care.

What to Expect at Your First Appointment

We will take a thorough history, paying close attention to the pattern, timing, and nature of your symptoms, since these differ meaningfully between the three types. We will carry out a hands-on assessment of your posture, scalene and pectoral muscles, scapular movement, and first rib mobility, an area research shows is often under-assessed. Crucially, if anything in your history or examination suggests a possible vascular cause, we will refer you promptly for urgent medical assessment, as this is not something we would treat directly.

Frequently Asked Questions

How do I know which type I have? The pattern of symptoms differs considerably, neurogenic TOS tends to cause gradual numbness, heaviness, and tingling, whilst venous and arterial TOS more often cause visible changes in the arm such as swelling, discolouration, or coldness, sometimes appearing suddenly. A thorough assessment helps clarify this, and any concerning features will always be referred on promptly.

Will I need surgery? For neurogenic TOS, most people improve with physiotherapy and targeted exercise, with surgery reserved for cases that don't respond. For venous and arterial TOS, surgery is more frequently required as part of appropriate medical management.

Can I keep exercising? For nTOS, gentle, targeted exercise is genuinely beneficial, but intensive aerobic activity may worsen symptoms by overworking the scalene muscles. Your practitioner will guide what's appropriate for you.

Is this the same as a trapped nerve in the neck? Not quite. Whilst both involve nerve compression and can cause similar arm symptoms, cervical radiculopathy (covered in our trapped nerve blog) involves a nerve root compressed within the spine itself, whereas nTOS involves the brachial plexus being compressed further down, between the scalene muscles and first rib, after the nerves have already exited the spine.

Recognise these symptoms? Get in touch using the contact form and we will carry out a thorough assessment, and ensure you're referred promptly for further investigation if anything suggests a vascular cause.

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References

1. Thoracic outlet syndrome. NHS. Available at: https://www.nhs.uk/conditions/thoracic-outlet-syndrome/

2. Recognising and managing thoracic outlet syndrome in primary care. British Journal of General Practice. 2026;76(764):141. Available at: https://bjgp.org/content/76/764/141

3. Digital Biomarkers for the Objective Assessment of Disability in Neurogenic Thoracic Outlet Syndrome. PMC. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8619444/

4. Thoracic Outlet Syndrome, United Kingdom: A Retrospective Review of Practice. Annals of Vascular Surgery. 2025. Available at: https://www.annalsofvascularsurgery.com/article/S0890-5096(25)00060-3/pdf

5. Neurogenic Thoracic Outlet Syndrome: a Scoping Review. Hand Therapy. 2026, summarised via Physiotutors. Available at: https://www.physiotutors.com/research/neurogenic-thoracic-outlet-syndrome/

6. Exploring the assessment, diagnosis and conservative management of patients with neurogenic thoracic outlet syndrome (NTOS): an online survey of UK medical and allied health professionals. Journal of Vascular Societies Great Britain and Ireland. 2023;3:35-45. Available at: https://jvsgbi.com/exploring-the-assessment-diagnosis-and-conservative-management-of-patients-with-neurogenic-thoracic-outlet-syndrome-ntos-an-online-survey-of-uk-medical-and-allied-health-professionals/

7. Management of Thoracic Outlet Syndrome. Physiopedia. Available at: https://www.physio-pedia.com/Management_of_Thoracic_Outlet_Syndrome

8. Exercise rehabilitation for neurogenic thoracic outlet syndrome: a scoping review. PMC. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9103635/

9. Exercise rehabilitation for neurogenic thoracic outlet syndrome: a scoping review. ResearchGate. Available at: https://www.researchgate.net/publication/362062254

10. Arterial Thoracic Outlet Syndrome Treated Successfully with Totally Endoscopic First Rib Resection. PMC. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5563393/